Electromagnetic gauge means including a motor-driven roller for measuring the caliper of a moving web



5, 1970 s. R. MOUNCE 3,525,929

ELECTROMAGNETIC GAUGE MEANS INCLUDING A MOTOR-DRIVEN ROLLER FOR MEASURING THE CALIPER OF A MOVING WEB Filed May 8, 1967 00 41 s zm V CA/l/fi/P/V' T I 4;

United States Patent 3,525,929 ELECTROMAGNETIC GAUGE MEANS INCLUD- ING A MOTOR-DRIVEN ROLLER FOR MEASUR- INC THE CALIPER OF A MOVING WEB George Ralph Mounce, Willowdalc, Ontario, Canada, as-

signor to Electronic Automation Systems, Inc., Grand Island, N .Y., a corporation of New York Filed May 8, 1967, Ser. No. 636,791 Int. Cl. G01r 33/00 U.S. Cl. 324-34 6 Claims ABSTRACT OF THE DISCLOSURE Electromagnetic reactor, reluctance gap measuring apparatus comprising magnetically permeable head and shoe members for engagement with opposite sides of a nonmagnetic traveling web, such as a web of paper, a reactor coil in one of said members establishing a magnetic circuit between said members in which circuit the web constitutes the reluctance gap, means for determining the reluctance gap in the magnetic circuit whereby to measure the caliper or thickness of the web, means for engaging said members with the opposite sides of the web and moving the same across the web in the direction transverse to the direction of the web travel to obtain a caliper profile of the web; characterized in that one of said members is a roller equipped with a drive motor to expedite damagefree engagement of both of said members with the web.

BACKGROUND OF THE INVENTION In the copending application of John B. Kahoun, Ser. No. 313,476, filed Oct. 3, 1963, now Pat. No. 3,411,075, gauge means of the general character is disclosed which is characterized by the combination of electromagnetic reluctance gap measurement of web caliper and retention of the head and shoe members in engagement with the opposite surfaces of the Web by magnetic attraction between said members, i.e., magnetic holding. Said application also discloses apparatus for positioning the two members adjacent the opposite surfaces of a web, moving the members into engagement with the web and then moving the two members across the web, while engaged with the web, to obtain the caliper profile thereof.

Considerable difficulty was encountered in initially engaging the members with the web without damaging the web, especially breaking the web in a papermaking machine, and said application contains a substantial disclosure concerning mitigation of said difiiculty.

Subsequently, as disclosed in the copending application of John B. Kahoun and Gary D. Stout, Ser. No. 511,663, filed Dec. 6, 1965, now Pat. No. 3,462,680, further mitigation of said difiiculty was attained by making one or both of said members in the form of a roller having rolling contact with the web in the direction of web travel. According to tihs disclosure, said roller was formed to have minimum inertia and it was set into rotation by engagement of the same with the traveling web. In the specific embodiment, and to afford optimum mitigation of web damage, at least the upper of the two members is a roller and programming apparatus is provided to first engage this roller with the upper surface of an unsupported portion of the web to bring the roller up to web speed, second, to separate the upper roller from the web while permitting it to continue rotating, third, to bring the lower member into engagement with the lower surface of the web (and if also a roller, to permit it to come up to web speed), fourth, to lower the rotating upper roller onto the portion of the web now supported by the lower member, and finally, cause the two members to conjointly traverse the web.

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While this apparatus and the described mode of operation thereof effectively prevented damage to the web, disadvantages were inherent in the complex programing of the operation and said programing rendered said gauge means incompatible for conjoint operation with other web profiling instruments.

SUMMARY OF THE INVENTION The subject of this invention is the provision of gauge means as aforesaid including means for driving the roller member up to web speed before contact with the web, and programing apparatus for simply moving the roller member into and out of engagement with the web without necessity for moving the other member. The advantages include faster, more reliable initiation of the measurement cycle, less liklihood of damage to the web, and compatibility with other web profiling instruments whereby a plurality of instruments may simultaneously be moved across a web by single traversing mechanism.

THE DRAWINGS FIG. 1 is a side elevation of a preferred embodiment of the web caliper measuring device provided according to this invention;

FIG. 2 is a front elevation thereof; and

FIG. 3 is a top plan view of the lower, reactor carrying member of the device.

DESCRIPTION In the illustrated embodiment of the invention, a roller 1, of soft iron, is mounted in a yoke 2 and rotates in bearings 3 and 4. The surface of the roll is ground to a fine finish and is usually covered with a thin film of chrome to provide good wear qualities.

One leg of yoke 2 is relatively enlarged and provided with a cylindrical bore for reception and mounting of roll driving means. Specifically, within said leg of the yoke, one of the roller shafts 5 is connected through a flexible coupling 6 to the shaft 7 of an electric motor 8. The motor is supplied with power through leads 9.

The yoke 2, which supports the roller and the motor, is mounted on a supporting arm 10. At the end opposite from the yoke 2, the supporting arm 10 is mounted by a bearing assembly 11 to a portion 12 of a conventional Web traversing mechanism (not shown). The bearing assembly 11 is such as to accommodate rotation of the arm 10 about the longitudinal axis of the arm 10 and swinging movement of the arm in the vertical plane of the latter axis toward and away from the upper surface of the web W.

Connected to a mid point of the supporting arm 10 is a cam follower 13 having an opening therein for reception of a rotary eccentric cam 14 having a V groove in the peripheral surface thereof. The upper marginal part of the cam follower rides in the V of the cam 14 and is normally held in engagement therein by the weight of the follower 13, arm 10 and motor driven roller assembly. The cam 14 is supported on a shaft 15, which in turn is journalled in a bearing 16 mounted on the part 12 of the traversing mechanism. The position of cam 14 as shown in FIG. 1 is such that the roller is resting on the upper surface of the web W. If cam 14 is rotated in the clockwise direction, cam follower 13 will be lifted, thereby raising the roller assembly from the web.

Disposed beneath the web and usually in continuous engagement therewith is a reactor head member 18 mounted on another part of the traversing mechanism for conjoint movement with the roller assembly 1 transversely of the web W. As shown in FIG. 2, the lead end of the head in the direction of traversing movement is inclined so as to facilitate non-damaging traversing movement of the head relative to the web. The head 18 otherwise consists essentially of a flat plate of soft iron having a slotlike recess 19 in its upper surface within which a reactor coil 20 is embedded. The upper surface of the shoe is ground to a fine finish and is usually plated with a thin film of chrome to provide good wear qualities. The characteristics of the coil 20 and its functioning have been described in the above identified copending applications. Also, as there described, the lower member may be a roller.

As shown in FIG. 3, the slot 19 in which the coil 2! is embedded is rectangular in shape and the two members 1 and 18 are positioned so that the line of contact of the roller 1 lies across the center of the coil slot 19 as indicated by the dotted line in FIG. 3. The roller 1 thus constitutes a permeable shoe member forming a portion of a magnetic circuit bridging the magnetic material of the head member or plate 18 surrounding the coil 20. The reluctance of the magnetic path surrounding the coil is thus influenced by the distance between the roller shoe and the head member as caused by the thickness of the intervening non-magnetic web. The reluctance of the magnetic path in turn influences the inductance of the coil. The coil is connected by wires 21 to a measuring circuit for converting inductance change of the coil into an electrical measurement or control signal, all as described in the previously identified copending applications.

The coil 20 is designed of rectangular shape to prevent minor movement of the roller 1 with respect to the head 18 in a direction at right angles to the axis of the roller from introducing a significant change in the inductance of the coil for a fixed spacing between the roller and the head.

Consider now the action of the system at the beginning of the caliper measurement. Cam 14 would be in a position rotated 180 from that shown in FIG. 1. The follower 13 would be engaged in the V groove of the cam and resting therein so that the roller assembly would be held well above the head 18.

Due to the V groove, the follower 13 controls the disposition of the arm 10 and the roller assembly 1 both as to elevation above the web and attitude toward the web, i.e., it holds the roller with its axis substantially parallel to the web. At this time, the web W would be riding over the head 18 in contact with it. Initiation of a caliper measuring cycle consists of simultaneously applying power to the mo tor 8, through leads 9 from a motor control circuit, to start the roller 1 spinning. At the same time, cam 14 is caused to rotate relatively slowly in a counter-clockwise direction. Under these conditions, roller 1 is accelerating and at the same time moving toward the web. Cam 14 is rotated at a rate such that by the time the roller 1 makes contact with the web, it has accelerated to the point where its peripheral speed is equal or at least close to the velocity of the web. Thus, when contact is made with the web, the relative velocity between the surface of the roll 1 and the web is near and little or no restraining force is applied to the web. The cam 14 continues to turn to the position shown in FIG. 1. Before this point is reached, the cam loses contact with cam follower 13, and the roller shoe assembly rests fully on the portion of the web supported by the head 18. The roller may continue to be driven by the motor 8 or may be rendered free rolling after engagement wtih the web.

During descent of the roller shoe assembly, the V- machined in the cam 14 holds the follower 13 vertically above the arm 10, thus maintaining the roller 1 with its axis horizontal or parallel to the head 18 and web W. When the cam loses contact with the follower 13, the hearing 11 accommodates rotation of the supporting arm whereby the roller is free to float up and down and to tilt relative to the web so that it will assume a position on the web providing even contact pressure over the length of the roller and will accommodate passage between the roller and the head of irregularities in the web such as lumps, holes, impurities, etc., without rupturing or tearing the web.

After the roller has been contacted with the web, caliper measurements may be performed. At the end of a traverse, or in the event of an emergency such as a break in the web, cam 14 is quickly turned to almost instantly raise the roller 1 out of contact with the web.

The cam 14 may be driven by an electric motor, or by a solenoid or other similar devices (not shown) capable of providing a controlled speed in one direction and a rapid return for the purposes above described.

A complete traverse of the head and roller shoe is usually made from adjacent one edge to adjacent the opposite edge of the web thereby to provide a cross-machine profile of the caliper of the web. At the end of the traverse, the roller is raised from the web and the roller and the head are returned to starting position with the roller out of contact with the web. In the preferred embodiment, the lower head member is maintained continuously in engagement with the web, but it is feasible to engage and disengage the lower member from the web when dealing with particular or problematic web materials.

By virtue of the positive drive provided by the motor 8, the apparatus of the invention is readily programmed for convenient operation and especially for conjoint operation with other web profiling devices. Specifically, by virtue of the invention, the caliper gauge can be integrated in a common traversing mechanism with basis weight, moisture and formation testing equipment. Also, by virtue of the invention, substantially all paper webs can now be profiled. For example, one of the most difficult applications is on newsprint where the web is weak, has frequent imperfections and is traveling at exceptionally high speeds. Two installations of the apparatus of the invention have been made on newsprint machines, and in both cases, the apparatus has produced zero breaks. Thus, the objects and advantages of the invention have been shown to be attained in a convenient, economical and practical manner.

While a preferred embodiment of the invention has been shown and described, it is to be appreciated that various changes, rearrangements and modifications may be made therein without departing from the scope of the invention, as defined by the appended claims.

What is claimed is:

1. In a device for determing caliper of a moving web of non-magnetic sheet material by measurement of the reluctance gap introduced by the sheet into a magnetic circuit formed by a caliper head member containing an electro-magnetic reactor contacted with one side of the material and a magnetically permeable shoe member opposed to the reactor and contacted with the other side of the material, one of said members comprising a roller mounted for up and down movement relative to the web, and means for engaging said roller with and disengaging the same from the web by up and down movement relative to the web, the improvement comprising motor means for driving said roller up to a peripheral speed substan tially equal to the velocity of the web prior to engagement of the roller with the web, the other of said members being continuously engaged with the web, a yoke mounting said roller for rotation, said yoke including an enlarged yoke arm having a recess therein, said motor means comprising a motor mounted in said recess, a coupling in said recess connecting said motor to said roller, a supporting arm for supporting said yoke, bearing means mounting said supporting arm for rotation about the longitudinal axis of said arm and for movement of said yoke toward and away from the web, and actuating means cooperating with said supporting arm for mov ing the latter to move said yoke toward and away from the web, said actuating means when in one position serving to support said roller in spaced parallel relation to the web and when in a second position serving to accommodate free floating up and down and tilting movement of said roller relative to the web.

2. In a device for determining caliper of a moving web of non-magnetic sheet material by measurement of the reluctance gap introduced by the sheet into a magnetic circuit formed by a caliper head member containing an electro-magnetic reactor contacted with one side of the material and a magnetically permeable shoe member opposed to the reactor and contacted with the other side of the material, one of said members comprising a roller mounted for up and down movement relative to the web, and means for engaging said roller with and disengaging the same from the web by up and down movement thereof relative to the web, the improvement comprising motor means for driving said roller up to a peripheral speed substantially equal to the velocity of the web prior to engagement of the roller with the web, a yoke mounting said roller, an arm supporting said yoke, bearing means mounting said arm for rotation about the longitudinal axis of said arm and for movement of said yoke toward and away from the web, a cam follower connected to said arm, and a V-grooved cam engageable beneath a portion of said cam follower in supporting relation therewith for moving said arm to move said yoke toward and away from the web, said follower when engaged with the V-grooved cam supporting said roller in spaced parallel relation to the web, said cam being spaced from said follower when said roller engages the web to accommodate free floating up and down and tilting movement of said roller relative to the web.

3. In a device as set forth in claim 2, said cam comprising a rotary eccentric cam.

4. In a device as set forth in claim 2, drive means connected to said cam for dual-speed operation of said cam to slowly move the roller toward the web and to rapidly move the roller away from the web.

5. In a device for determining the caliper of a moving web of non-magnetic sheet material by measurement of a reluctance gap introduced by the sheet into a magnetic circuit formed by a caliper head member containing an electro-magnetic reactor contacted with one side of the material and a magnetically permeable shoe member opposed to the reactor and contacted with the other side of the material, means mounting one of said member with freedom for up and down and tilting movement relative to the web, and means for engaging said one member with and disengaging the same from the web by up and down movement thereof relative to the web, the improvement wherein said last named means consists essentially of an arm supporting said one member, bearing means mounting said arm for rotation about the longitudinal axis of said arm and for movement of said one member toward and away from the web, a cam follower connected to said arm, and a V-grooved eccentric cam engageable beneath a portion of said cam follower in supporting relation therewith for moving said arm to move said one member toward and away from the web, said follower when engaged with the V-grooved cam supporting said one member in spaced parallel relation to the web, said cam being spaced from said follower when when said one member engages the web to accommodate free floating up and down and tilting movement of said one member relative to the web.

6. In a device as set forth in claim 5, drive means connected to said cam for dual-speed rotation of said cam to slowly rotate the cam to move the roller toward the web and to rapidly rotate the cam to move the roller away from the web.

References Cited UNITED STATES PATENTS 2,474,117 6/1949 Rendel.

FOREIGN PATENTS 408,340 4/1934 Great Britain.

OTHER REFERENCES Kahoun, J.; The Development of an On-Machine Caliper Profiler; Pulp and Paper Magazine of Canada, March 1965, pp. T195T-200.

GERARD R. STRECKER, Primary Examiner R. J. CORCORAN, Assistant Examiner U.S. Cl. X.R. 162263; 33147 

